With the price of oil climbing ever upward, I am becoming more interested in the prospect of switching from heating oil to natural gas. We already have gas in the house for the stove and clothes dryer. We have a 12 year old Burnham oil fired furnace, with hot water radiators.

Has anyone here done it? What is involved and what was the payback period?

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We converted from heating oil to natural gas two years ago. When we moved in the existing furnace was venting CO into the house, so I needed to do something. We were lucky since, even though there were no natural gas appliances in the house, the gas line went right to the home (I just needed to have the line tested and a meter installed, then add the lines inside.

I had a plumber do the gas line work, and I installed the furnace myself. It was not an easy job (cutting/fitting te ductwork was the worst of it).

Savings: We are saving a lot of money due to the conversion, mostly because I also scrapped our electric water heater and put in a gas one. The old oil furnace was approx 70% efficient, the new gas furnace is 93% (and the ones on the market now that qualify for the federal rebate are 95%).

The good news is that you've already got NG running into your house, so that will greatly reduce your expense (provided the service is adequate for running a furnace, which it probably is). Do you want to continue to use your radiators (i.e. do you want to install a natural gas boiler) or do you want to convert to a forced air heating system? It would be cheaper to stick with the water-based system, and I believe it might be possible to set things up to also provide your domestic hot water at the same time (which is a lot cheaper than heating water with electricity). If you are happy with the radiators, then there's no only real advantage to converting to forced air unless you also want to install central air conditioning at the same time.
Note that the high-efficiency furnaces and boilers take in air from the outside and vent to the outside through PVC pipes, so those ducts will need to be run, but that's usually not very hard to do.

Heating oil prices and propane prices are expected to be very high this winter, while NG prices are expected to rise far less. But, things could be different in the future.

Advantages of getting rid of the oil burner: Less annual maintenance for the equipment, no chance of an oil leak and al the environmental badness that goes with it, the fumes of heating oil are no longer permeating my garage, and I regained 10 sq feet of floor space in my garage where the tank used to be.

Unless you are handy and itching for a big project, this is something to contract out. It's got all the elements: electricity, sharp metal, explosive gases. Woo hoo!

I just took a look at the equipment prices. A 70K BTU 90+% efficient hot water unit is approx $3600, while a similarly sized conventional furnace is approx $1000. Still, unless you want central AC or have some other reason to install ductwork, it would probably be cheaper overall to stick with your radiators than to have the ducts installed (unless your house is very simple in design).

Samclem: Thanks, this seems less expensive than I thought it would be. We already have the hot water tank attached to the furnace (it is set up like a separate zone), so I guess we just really need the furnace itself. Changing to forced air is a virtual impossiblity, given that the house is 150 years old. We rarely need air conditioning. On the hottest nights in the summer, we use a small window unit in the bedroom.

I didn't know that one would need a separate intake duct. My furnace is in the cellar, so running a duct is not difficult, although if it is required to be set above ground by a certain hieght, that could be a problem.

The gas company just sent me a card in the mail inviting me to call to talk about the switch. I think I will.

I didn't know that one would need a separate intake duct. My furnace is in the cellar, so running a duct is not difficult, although if it is required to be set above ground by a certain hieght, that could be a problem.

Gumby,
The new high efficiency boilers (which is what you want) always take their combustion air directly from outside. This is one of the things that heps them increase their efficiency, since they aren't sending gobs of your "already-paid-to-heat-this-toasty-air-in-my-home" air up the flue. If the boiler is on or near an outside wall inthe basement, this should be an easy thing. The intake and exhaust air will either run side-by-side in plastic pipes our through a special larger concentric pipe through the wall and outside. They can terminate a few feet above the ground, and they can just stick right out of the wall (with an appropriate cap), there's no need for a tall stack outside. The installer can take a look at things and tell you in a minute the best way to get this done.

Computing payback: Since you already buy both NG and fuel oil locally, you can look on your bills to see the local prices for each. Natural gas produces (ideally) 100,000 BTU per therm, fuel oil produces (ideally) 138,000 BTUs per gallon. Your present oil-fed boiler is probably 80% efficient (it might be even less) and your new NG boiler will be at least 90% efficient.

With the info above, you should be able to compute cost comparisons.

One other thing: Be sure to buy the right size boiler. It would be best if the technician did a heat load study on your house rather than just looking at the data plate on your present boiler or using a rule of thumb ("Oh, a 2000 sqare fot hose in this county needs a 90,000 BTU boiler."). I had three HVAC guys give me estimates when I swapped out my equipment, and all of them just wanted to sell me the same size furnace I had initially (which would have been 50% too big since I'd changed out windows and upgraded the insulation). It doesn't take much time to do the calculations--you'll know they are probably doing it right if they ask about your attic and wall insulation and if they take a close look at your windows.

I saw some interesting stuff about boilers with storage tanks that also heat your water on demand. I think the one I saw was a "system 2000". Seemed to be pretty well regarded and I noted that they went to a lot of trouble to not talk about the prices, so I suspect they're ridiculously expensive.

The new high efficiency boilers (which is what you want) always take their combustion air directly from outside. This is one of the things that heps them increase their efficiency, since they aren't sending gobs of your "already-paid-to-heat-this-toasty-air-in-my-home" air up the flue.

samclem, I've read that, it always seemed to make good sense, and I was ready to 'convert' my furnace and water heater to draw outside air - build a closet around it, bring in a duct from outside, test for and take precautions to prevent back-draft. Or at least to buy vented units when I need to replace them.

Then I started thinking ( I seem to prefer thought to work )...

does this really help? There is no free lunch. Let's say it is 30F outside and 65F inside. W/o outside vent, the furnace leaks in air and heats it to 65F and sends some of it up the flue. But WITH an outside vent, it is drawing in 30F air instead of 65F air - doesn't that cooler air cool the combustion chamber and force the furnace to run longer? in essence, it seems that the air needs to be heated, either way.

It might be more comfortable with an outside vent - you might reduce drafts in living spaces from air leaks due to the draw, but I wonder if efficiency is really improved much?

We have a natural gas boiler for our hot water system. The boiler was replaced a few years ago, the cost is going to depend in part how many square feet you have to heat, the type of house, and what part of the country you are in. As SamClem says, be sure to get good people to size your boiler. Your gas company may help. Our boiler direct vents to the outside using stainless steel piping. Code here requires outside air for combustion as well.

Just not having to deal with a fuel oil tank would make it worth it to me.

In our part of the country most people switched to natural gas some years ago as the cost was a lot less and our heating costs tend to be high.

[quote=samclem;566978]Gumby,
Computing payback: Since you already buy both NG and fuel oil locally, you can look on your bills to see the local prices for each. Natural gas produces (ideally) 100,000 BTU per therm, fuel oil produces (ideally) 138,000 BTUs per gallon. Your present oil-fed boiler is probably 80% efficient (it might be even less) and your new NG boiler will be at least 90% efficient.

With the info above, you should be able to compute cost comparisons.
quote]

In my area, gas is $1.78 per Ccf plus $8.25 month. Oil is about $2.80 per gallon and we currently use about 1000 gallons per year. If I have done the math correctly (I used 102.5k BTU per Ccf for gas and 140k BTU per gal. for oil), I should save about $270 per year just by switching fuel sources. I realize that this probably will vary as the relative prices of gas and oil fluctuate.

The efficiency gain would be a separate calculation, since I'm sure a new oil boiler would also be much more efficient. I calculate a 15% efficiency gain would save another $380 per year, which implies about a 6 year payback based on the price you cited.

Let's say it is 30F outside and 65F inside. W/o outside vent, the furnace leaks in air and heats it to 65F and sends some of it up the flue. But WITH an outside vent, it is drawing in 30F air instead of 65F air - doesn't that cooler air cool the combustion chamber and force the furnace to run longer?
It might be more comfortable with an outside vent - you might reduce drafts in living spaces from air leaks due to the draw, but I wonder if efficiency is really improved much?

-ERD50

I did some research on this when installing my wood stove years ago. In that case, providing outside air for combustion significantly reduced drafts in other areas of the house caused by the negative relative indoor air pressure due to the stove sucking combustion air and sending it up the stack.

I also noted that they said your stove does not burn cooler because the combustion air is cooler. The temp of the flame is about the same whether the combustion O2 is cool or warm.

Perhaps that would be true for natural gas as well?

__________________
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I did some research on this when installing my wood stove years ago. In that case, providing outside air for combustion significantly reduced drafts in other areas of the house caused by the negative relative indoor air pressure due to the stove sucking combustion air and sending it up the stack.

I also noted that they said your stove does not burn cooler because the combustion air is cooler. The temp of the flame is about the same whether the combustion O2 is cool or warm.

Perhaps that would be true for natural gas as well?

I can understand the draft/comfort issue. It might even be the most important part of it. Or maybe it is ALL of it?

But the idea that you get the same heat out whether the combustion air is 30F or 65F just doesn't pass muster with me. Sure, the flame itself might be the same temperature - I guess physics defines combustion temperatures, but I would still think the total heat energy put out by the furnace would be less. How could it not be - less energy in must mean less energy out, right?

A lot of furnaces and boilers that use direct vent outside air sources preheat the air with captured heat from the exhaust/flue. Colder outside air is denser than warmer inside air, so less of it is needed for combustion.

Slight inefficiency and transfer loss is way better than sucking cold air in through every crack and seam throughout the living area...in that case you're warming all of that air anyhow instead of having it slightly reduce the efficiency of the burner.

Gumby as an alternative you could explore installing a gas burner in your existing Boiler. There are several gun type gas burners available in the market some of which would be compatible with your boiler. Burnhman may even have a gas fired version of your existing boiler. If you go this route I'd recommend installing a flue damper which opens when the boiler is running and closed when it is not. Contact a couple of good heating contractors in your area and ask if they do these type of conversions. Not knowing your labor rates the equipment should be in the $1000 to $1500 range. Your boiler is probably good for another 30 years.

__________________USCG regulations say you have to go out. They don't say anything about coming back.

I calculate a 15% efficiency gain would save another $380 per year, which implies about a 6 year payback based on the price you cited.

Six year payback would be super. Remember, though, that the price i cited was for the equipment only, so you should prepare yourself for a higher bill to have the installation done.

Still, I'll bet you'll find it's a good deal. Unfortunately, winter's right on our doorstep so you may not find any hungry HVAC guys willng to give you a great price.

ERD: I agree that the separate makeup air thing is primarily driven by safety. It is really easy to get a backdraft in modern house--just turn on the clothes dryer or the stove exhaust hood and it's virtually guaranteed to cause a backdraft in a very tight house. Still, by not causing a bunch of 30 deg F air to have to infiltrate the building envelope, I think it is a gain compared to the 30 deg diff in the temp of the combustion section. Not a big gain: It is amazing how cool the exhaust gases from these furnaces are, they are really extracting almost all of the available energy of combustion, and that 30 deg F difference in combustion temp would have produced a difference at the registers in the rooms.

Note: Although these furnace have small fans to bring in the combustion air, they are fairly intolerant of ambient pressure differences at the intake point and the exhaust point. For this reason, they are normally located close together, but oriented so the exhaust gases don't get "inhaled" by the intake. It is not permissible to put the tubes on separate sides of the house or opposite sides of a roof since a breeze could upset the pressure balance required.

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